Regarding the cellular service, if you have CDMA compatible phones then there is service in most Yukon communities.
4G service in Whitehorse and it was recently introduced in Dawson City too. iPhones & iPads aren't great here, unless you live in the city!
With a CDMA compatible device & service, then your cell can be used along the Alaska Highway in Watson Lake, Teslin, Whitehorse, Haines Junction, Destruction Bay and Beaver Creek. On the North Klondike there is CDMA service in Carmacks and Pelly Crossing.
WiFi can be iffy at some RV Parks in Yukon. Bandwidth isn't cheap in Yukon and the major supplier has caps on usage. As well, the infrastructure is aging and not reliable. During the past year, there have been numerous blackouts due to servers failing and lines being damaged.
Satellite phones are somewhat reliable, but not 100%. Being this far north the satellites aren't always in view. Trees and mountains get in the way. Our home satellite dish is pointed directly at the horizon to the southeast. The dish installer was worried that the trees would interfere.
Regarding pictures, either carry lots of memory cards for your camera OR have a USB external hard drive. Western Digital has some nice small external drives (the My Passports) that have proven very reliable for me despite being bounced around and accidently dropped. I like them because they are small and USB-powered. Comes in handy when drycamping. I use these for image backup. I save to both my laptop and the external drive. Once had my laptop fail near Watson Lake so was grateful to have the images on the external backup too. When I return home it is a simple matter to copy the thousands of images from the WD My Passport to my desktop computer.
BTW, this is how the Alaska Highway looked Tuesday January 29, west of Whitehorse, at -30C (-22F)
Here the Alaska Highway crosses the image left to right about half way up. Those are fox tracks lower left